Solvent extraction process



Patented Feb. 24, 1953 UN IT E D PATENT O F F I CE.

,rationof .New York Application October '25, 1949!,.ScliaLNo- .123#154 9 Claims. (Cl.l

This invention has-todo withiasolvent lextrae-- tion process. More specifically, theinventionhas to do with Va process for .selectively v:sepaiaiting hydrocarbons and organic .oxygen L.cornpou'nds from mixtures containing fthe same.

During recent years, considerable attention has been given to `the .production of .organic :Oxygen compounds from hydrocarbonsfby incomplete 0.xidation of .the latter. Whilemanyof theoxdation processesdeveloped to.dat,e have .proven val.- uable for the production fof -oxysenated materials, such processes have been :iQuSly handicapped by the difiiculties .attending separation of the numerous hydrocarbons and .oxygenated materialsrpi esent inthe reactQIlJDrOducts. ,This is Well illustrated by processes .developed :Qr the oxidation of short Achain hydrocarbons such -as propane and butanes, wherein .a j.cornplexity :.Qf acids, alcohols, aldehydes, esters, ketonea ylactones, etc. are found in the .reaction products together with various hydrocarbons. Many ,of the hydrocarbons and oxygenated materials either have similar boiling points or yforniazeotropes such that simple distillation procedures are of no avail in providing a separation. C0111- plex distillation procedures, involving multiple azeotropic distillations for example, have been resorted to in order to Ysolve the problem, buit these involve considerable expense both in equipment and in operation. Chemical separation procedures have proven impractical in view of their extremely high cost. For example, an alkali or caustic treatment of ythe reaction products removes most of the acids, but does not effect a separation of other oxygenated materials. The separation problem is even more -dilicult when longer chain hydrocarbons, such as hexanes heptanes and octanes found `vin gasolines, are oxidized. In the latter case, oxygenated v`materials range from formaldehyde through eight carbon atom acids. In addition, -some cfu-'the hydrocarbons are cracked-or degraded and ypoly.- merized. Here again, distillation-and chemical separation procedures are impractical. AStilton.- other illustration, and one in which thesepara- -terials from -petroleum fractions.

2 tion problem is even more pronounced, iS the incomplete oxidation .of poraiiin waxes.-

...Inthe petroleum art, too. .there has been .for many .years the problem of .Separating Organic oxygen .compounds from various hydrocarbon fractions. ouch ,as paraiiijic and naniitheniomixtures containing relatively ,small quantities of acids, alcohols. aldehyoes, etc. .Distillatiorinroeodiires have not proven .effective in .removing the. Xygenatod materials .Chemical separation DIQQEQLITES .have @1.5.0 bel .0i little Value, a1- though alkali treatment has been eifective in removing acids., `but not other oxygenated matenais, from hydrocarbon fractions.

VConventional `selective solvents are either Aineffective ornot Well suited for therseparation under consideration here. For example, anili-ne and -nitrooenzene are completely rmiscible with most ofthe mixtures referredto above. Another Wellknown solvent, furfural, is not selectivewith such mixtures, for it extracts some hydrocarbons together with oxygenated materials -To date, therefore, -no lsimple Yand inexpensive selective solvent 1procedure has been developed `for separating `hydrocarbons and oxygenated materials of 1simi-larboiling range -f-rom `mixtures containing V4the same.

It is an-object of Jthis invention, therefore, -to provioean effective -means ifor separating hydrocarbons yand 4oxygenated v.materials oi .the ,same or similar .boilingrange It isralso an object vof .this invention ato selectively .separate -hydrocarbons :and acids, alcohols, .aldehydes testers, ketones, :lactones, `etc. from mixtures (obtained by rthe incompletefoxidation fof paramns. vA further obJectis-to provide substantially pure hydrocarbon fractions from hydrocarbon fractions con-- tainingioxygenated materials. .Still another object is ito selectively lseparate .oxygenated :ma-

Other -objects and advantagesof .the 4invention will be apparent from vthe follow-ing description.

Ithas now been lfound that acetonitrile is :se-

` lective -gin character and makes 'possible a separation of oxygenated -materials `from hydrocarbons of similar boiling range. Thus, it has been found that a mixture of organic oxygen compounds and hydrocarbons can be contacted with acetonitrile, whereupon the oxygen compounds are selectively extracted by the acetonitrile. The extract of oxygen compounds and acetonitrile can be resolved simply by distillation, for example, and the recovered acetonitrile can then be recycled. In the same vein, the recovered hydrocarbons can be recycled for further oxidation.

In addition to the mixtures of hydrocarbons and oxygenated materials described above, it will be apparent to those familiar with the art that numerous mixtures of such character may be used in the process of this invention. In general, however, the process is most advantageous with paraffin and naphthene hydrocarbons and their oxygenated derivatives of similar boiling range. It is particularly effective with those mixtures which boil above about 110 C., inasmuch as it has been observed that with a relatively high concentration of cyclohexane and/or methylcyclohexane in a mixture to be treated,

these cyclohydrocarbons are extracted by acetonitrile. Mixtures of olefins and oxygenated materials may also be resolved by the present process; with such mixtures, however, it is recommended that somewhat more emcient extraction equipment be used than is required for mixtures y,

containing paraffins and/or cycloparaiins. Typical olen-oxygenated material mixtures are those obtained by Fscher-Tropsch reactions, wherein carbon monoxide and hydrogen are reacted in the presence of cobalt or iron catalysts or the like and wherein a variety of hydrocarbons and oxygenated materials are formed.

The process of this invention can be employed either as a batch operation or a continuous process and, in the latter instance, the mixture to be' treated and the acetonitrile may flow concurrently or countercurrently in the contacting vessel. Acetonitrile and the mixture to be treated are mixed in a volume ratio of between about :1 and about 1:1 of acetonitrile to mixture. The

of water in the solvent, for example, 0 to 25 per-` cent of water, thereby increasing the solvents selectivity. While low temperatures below C. can be used by resorting to refrigeration, there is no advantage in so operating; in this respect the instant process is advantageous in that expensive refrigeration equipment is not required. With regard to contact between the mixture and the solvent, it is recommended that they be thor-l oughly agitate or interdispersed in order to assure that the equilibrium distribution coefcient is approached. In general, this requires at least about two to five minutes. The time of contact may be simply regulated in batch operations as will be recognized and, in continuous operations, the rate of iiow of the mixture and of the solvent can be readily regulated.

.A suitable system for carrying out a continuousv process in separating oxygenated materials and hydrocarbons from a mixture containing the same is shown in the accompanying diagram,.

where acetonitrile is introduced through conduit I at an upper portion of an extraction tower 2, and a suitable mixture is introduced through conduit 3 at a lower portion of the tower. The

acetonitrile and the mixture flow countercurrently as shown, and the bulk of the acetonitrile containing substantially all of the oxygenated materials is withdrawn from the bottom of the tower 2 through conduit 4.

The acetonitrile and oxygenated materials in conduit 4 are introduced into fractionator 5, wherein acetonitrile is distilled off and withdrawn through conduit l at the top of the fractionator. Acetonitrile in conduit I may be used again in extraction tower 2 or may be withdrawn from the system. It will be apparent that additional fresh acetonitrile may be introduced into the system in conduit l, through a suitable valve (not shown). The oxygenated materials are withdrawn at the bottom of the fractionator 5 through conduit 6. The hydrocarbons substantially free of oxygenated materials are withdrawn from the top of the extraction tower 2 through T. If necessary, the relatively small amount of acetonitrile contained in the hydrocarbon material can be readily removed by distillation in a suitable fractionator (not shown).

The following specific, and non-limiting, examples are representative of the results to be obtained in accordance with the process of this invention.

Example I A mixture of naphthenes and oxygenated naphthenes was extracted with acetonitrile and with conventional solvents, namely, aniline, nitrobenzene and furfural. The mixture contained cycloparafns, chiefly decahydro-naphthalene, and oxygenated cycloparaffins (aldehydes, alcohols and ketones). The properties of the mixture were: hydroxyl number of 29 milligrams of KOH per gram, equivalent to 5.2 per cent by weight of alcohols; carbonyl number of 54 milligrams of KOH per gram, equivalent to 9.5 per cent by weight of aldehydes and ketones; boiling range of 305-385 F. (152-196 C.).

One part, by volume, of the aforesaid mixture was contacted at 20-25 C. with two parts, by

i volume, of acetonitrile in a single stage extraction.

The extract of oxygenated material and acetonitrile was separated from the hydrocarbon or raffinate phase, and was distilled to remove acetonitrile therefrom. The extract comprised 23 per cent by volume of the original oxidation product. The results of the extraction are tabulated below. The alcohols were determined by hydroxyl number and formation of boric acid ester, and the aldehydes and ketones by carbonyl number.

With aniline as the solvent, it was found that aniline and the oxidation mixture were completely miscible, such that no separation could be effected. This was also found to obtain with nitrobenzene.

Furfural, as shown in the table, was effective in separating oxygenated material from the hydrocarbons; however, furfural was much less selective than acetonitrile. In effect, furfural extracted a substantial quantity of hydrocarbons together with oxygenated materials. Using the results shown in the table, it will be apparent that on a comparative basis acetonitrile is about 21A@ times as selective as furfural in removing oxygenated materials from the oxidation product, and that the use of furfural is not practical unless some means of recovering the furfural other .than distillation or bisulfite extraction is developed.

'LIABLE Solvent Acetonitrile Furfural v Aniline Nitrobenzene Wt. Percent Oxygenated Material in:

Ch 14. 7 14. 7 Completely mi'scible.- Gompletelyfmiscible.

' 58. Qy 'l an. Q ...-.v.,. Do.. Raf-friate b 2,4 6.5 D0. Wt. of Oxygenat E l eleqtwlty of Oxygeua Mmm-131m Charge 87 C!) f'^'-dQf'W-Wf^" DQ* Wt. Percent of Original Alcohol in- Extract. A 82 (l.) do D0. Railinate 18% 11': L. do Do- Wt. Percent Original Aldehydes and Ketones in:

xtract 91 D0- & 31` Do.. Vol. Yercent Extract- 23y l* 4,5 Do.. Solvent-to-Hydrocarbon B, 2:1 V2 :1 Doi.

e The furfural was removed from the extractby sodium bisulfate. Unfortunately, the bisulfite also extracted some hydrocarbon and practically all oi the,oxygenatedmatenals; thereforek when theniurfurel was reeoyelihit; contained hydrocarbon andf oxygenated material which could not easily be separated (since they boil in the same range). Thus cxt r a,c,tio11,with.furjuraldoes,1101 v yieldanyconcentrated oxygenated iraction.

b A second extraction removed all of thealcohol and all of the ketone? and aldehydes.,

Example II A heavy alkylate, obtained as; abyproductfrqm butylene alkylation operations, was incompletely oxidized, non-catalytically, with air at 500 F. and 300 pounds per square inch pressure, with a space velocity of 75 and a molar ratio of air to hydrocarbon of 3. The heavy alkylate had the following properties:

Specific gravity, A. P. I 46.4 Norwood bromine No 70.1 Iodine No. 39 Sulfur, percent 0.02 Flash point, F. 185 ASTM distillation, F.:

I. B. Pt. 407 433 435 30% 453 50% 470 70% 489 90% 530 End. Pt 599 The oxidation product thus obtained was extracted with a ten per cent aqueous solution of sodium hydroxide, whereupon acids contained therein were extracted. The acids comprised one percent of the product. The alkali-treated oxidation product (99 parts by volume) was then contacted at 25 C. with three parts by volume of acetonitrile containing sixteen percent of water. The extract of solvent and oxygenated material was then distilled to a maximum temperature of 101 C. to remove the aqueous acetonitrile solvent. In this way, an extract comprising 3.6 per cent of oxygenated material was obtained. The raffinate or hydrocarbon phase was substantially free of oxygenated materials.

The extract was fractioned into a fraction (1) boiling from 200 to 280 C. and a second fraction (2) boiling from 280 to 300 C. Upon analysis, fraction (1) was found to contain approximately 20 per cent alcohols and the remainder aldehydes and ketones. Fraction (2) contained more than 95 per cent alcohols, aldehydes and ketones. with the remainder being hydrocarbons.

Example III A naphthenic hydrocarbon charge comprising a mixture of monomethyl-, dimethyland trimethyl decalins, predominantly dimethyl, was incompletely oxidized under the following conditions: 525 F.; 100 pounds per square inch pressure; space velocity, 8; and molar ratio of air to hydrocarbon of: 6. The hydrocarbon charge had thefollowing properties:

f, Specific gravity 0.8708

Specific gravity, A. P. I. 31.0 Aniline No., F. 140 Refractive index 1.4710 ASTM distillation, F.:

I. B. Pt. (10 mm.) 122 (approx. 325

760 mm.) 10% 185 25% 212 50% 217 75% 230 248 (490 760) Residue--15% The oxidation product obtained was extracted at 25 C. with the aqueous acetonitrile described in Example II, using a continuous extraction technique in which the acetonitrile was continuously passed through a packed tower filled with oxidation product. The acetonitrile taken from the extraction tower was continuously separated from the extract by distillation, and was recycled. The oxygenated material thus obtained comprised ten per cent of the original oxidation product; this represented eighty per cent of the oxygenated material originally present in the oxidation product.

It is to be understood that the foregoing description and specic examples serve to illustrate the invention and that many variations and modications may be made therein without departing from the spirit and scope of the appended claims.

We claim:

1. In the process for producing valuable organic oxygen compounds from hydrocarbons. which includes partially oxidizing a hydrocarbon to produce an oxidation product containing organic oxygen compounds including acids and hydrocarbons of similar boiling range, and which includes separating said oxygen compounds including said acids from said hydrocarbon, the improvement which consists of the following sequence of operations: (a) contacting said mixture with acetonitrile; (b) establishing phase separation into an extract phase rich in said oxygen compounds including said acids, and a raffinate phase less rich in said oxygen compounds than said oxidation product; (c) separating the extract and raflinate; (d) removing said acetonitrile from the extract phase to provide a concentrate of said oxygen compounds including said Y acids.

2. The process of claim 1 wherein the volume ratio of said acetonitrile to said mixture is between about 1:1 and about 5:1.

3. The process of claim 1 wherein the mixture has a boiling point above about 100 C. and contains paraiins and oxygenated derivatives thereof of similar boiling point.

4. The process of claim 1 wherein the mixture has a boiling point above about 100 C. and contains olens and oxygenated derivatives thereof of similar boiling point.

5. The process of claim 1 wherein the mixture has a boiling point above about 100 C. and contains naphthenes and oxygenated derivatives thereof of similar boiling point.

6. The process of claim 1 wherein the mixture contains naphthenes and oxygenated derivatives thereof and has a boiling range of about .305- 385 F.

, 7. The process of claim 1 wherein the mixture contains paraffins and olens and oxygenated derivatives thereof and has a boiling range of about 433600 F.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Name Date Kozacik et al Sept. 19, 1950 OTHER REFERENCES Number 2,522,678

Hoerr et al., J. Org. Chem., vol. 9, Dp. 267-80 (1949).

Garland et al., ibid., vol. 8, pp. 344-57 (1943).

Hoerr et al., ibid., vol. 9, pp. 329-37. 

1. IN THE PROCESS FOR PRODUCING VALUABLE ORGANIC OXYGEN COMPOUNDS FROM HYDROCARBONS, WHICH INCLUDES PARTIALLY OXIDIZING A HYDROCARBON TO PRODUCE AN OXIDATION PRODUCT CONTAINING ORGANIC OXYGEN COMPOUNDS INCLUDING ACIDS AND HYDROCARBONS OF SIMILAR BOILING RANGE, AND WHICH INCLUDES SEPARATING SAID OXYGEN COMPOUNDS INCLUDING SAID ACIDS FROM SAID HYDROCARBON, THE IMPROVEMENT WHICH CONSISTS OF THE FOLLOWING SEQUENCE OF OPERATIONS: (A) CONTACTING SAID MIXTURE WITH ACETONITRILE; (B) ESTABLISHING PHASE SEPARATION INTO AN EXTRACT PHASE RICH IN SAID OXYGEN COMPOUNDS INCLUDING SAID ACIDS, AND A RAFFINATE PHASE LESS RICH IN SAID OXYGEN COMPOUNDS THAN SAID OXIDATION PRODUCT; (C) SEPARATING THE EXTRACT AND RAFFINATE; (D) REMOVING SAID ACETONITRILE FROM THE EXTRACT PHASE TO PROVIDE A CONCENTRATE OF SAID OXYGEN COMPOUNDS INCLUDING SAID ACIDS. 